For routinely RNA extraction out of 5ml whole blood I use the following
protocol:
First of all remove plasma, then add 5ml of 0.15M NH4Cl (8g/l), 0.01M KHCO3
(1g/l) (precooled to 4°C) and shake for 5min, centrifuge for 10min at 4°C
with 2.000g and pour away supernatant. Repeat steps if necessary and
dissolve cells in lysis buffer (e.g. TRIzol). Good luck!